This application claims priority under 35 U.S.C. Sec. 119 to No. 2000-297426 and No. 2000-297427 filed in Japan on Sep. 28, 2000, respectively, the entire contents of which are herein incorporated by reference.
1. Field of the Invention
The present invention relates to a vehicle motion control system for performing various controls such as a traction control, steering control by braking or the like, particularly relates to the vehicle motion control system having a pressure control valve device disposed between an automatic hydraulic pressure generating apparatus for generating a hydraulic braking pressure irrespective of operation of a brake pedal and each wheel brake cylinder, and controlling the automatic hydraulic pressure generating apparatus in response to the condition of the vehicle motion and controlling the pressure control valve device, to perform an automatically pressurizing control to the wheel brake cylinder.
2. Description of the Related Arts
In Japanese Patent Laid-open Publication No. 2-241863, which corresponds to the European Patent No. EP0379329A2, there is disclosed a fluid-pressure operated booster which is controlled solely by operation of a solenoid-operated valve means in response to a signal from an electric controller, and a vehicle braking system having the booster. In that publication, it is so described that should, for example, a wheel speed sensor emit a signal indicative of a xe2x80x98wheel-spinxe2x80x99 condition then, in a normal inoperative position of the pedal, the controller operates the solenoid-operated valve means independently of the pedal to apply the brake on the spinning wheel.
According to the vehicle control system as disclosed in the above publication, however, a pressurizing condition and a non-pressurizing condition are repeated by automatically pressurizing means such as a booster, whereby its operating sound is made so large as to cause a noise, and energy consumption of the automatically pressurizing means, e.g., vacuum consumption (when the vacuum booster is employed), is made large.
In order to solve the above-described problem, the number of repetition of the operation and non-operation of the automatically pressurizing means can be reduced by delaying the timing for stopping operation of the automatically pressurizing means, and performing a delay control to shut off the communication between the automatically pressurizing means and wheel brake cylinders, and eventually the energy consumption can be reduced. While the delay control is being performed, however, the hydraulic braking pressure is not supplied to the wheel brake cylinders according to the system as disclosed in the above publication. Therefore, it is necessary to provide an immediate action when a brake pedal is depressed during that period.
Preferably, the period for performing the delay control may be adjusted in response to a tendency of initiating the automatically pressurizing control, as it may be adjusted to be long in such a condition that the automatically pressurizing control is likely initiated, otherwise it may be adjusted to be short.
Accordingly, it is an object of the present invention to provide a vehicle motion control system for performing an automatically pressurizing control to wheel brake cylinders at least when a brake pedal is not depressed, wherein an appropriate delay control is performed in response to a tendency of initiating the automatically pressurizing control, to reduce a noise caused by repetition of a pressurizing condition and a non-pressurizing condition, and reduce energy consumption effectively.
It is another object of the present invention to provide the vehicle motion control system, wherein the noise and energy consumption are reduced effectively, and wherein when the brake pedal is depressed while the automatically pressurizing control is being performed, the hydraulic braking pressure is immediately supplied to the wheel brake cylinders.
In accomplishing the above and other objects, the vehicle motion control system includes wheel brake cylinders which are operatively associated with wheels of the vehicle, respectively, an automatic hydraulic pressure generating apparatus for generating a hydraulic braking pressure irrespective of operation of a brake pedal, a hydraulic pressure control valve device which is disposed between the pressure generating apparatus and the wheel brake cylinders to control the hydraulic braking pressure in each wheel brake cylinder, and a controller which is adapted to control the pressure generating apparatus and the valve device in response to conditions of vehicle motion, and perform an automatically pressurizing control to the wheel brake cylinders at least when a brake pedal is not depressed, thereby to perform a vehicle motion control. The controller is adapted to maintain the pressure generating apparatus to operate for a predetermined time period after the vehicle motion control was terminated, and control the valve device to shut off the communication between the pressure generating apparatus and the wheel brake cylinders, to modify the time period on the basis of the conditions of vehicle motion. Thus, a tendency of initiating the automatically pressurizing control can be determined, so that by adjusting the predetermined time period in response to the conditions of vehicle motion, a delay control can be performed in response to the tendency of initiating the automatically pressurizing control.
In the system as described above, the tendency of initiating the automatically pressurizing control for the traction control and the steering control by braking can be determined especially on the basis of an accelerating condition of the vehicle, out of the conditions of vehicle motion. Therefore, the vehicle motion control system may further comprise an acceleration detection device for detecting the accelerating condition of the vehicle. In this case, the controller may be adapted to modify the time period at least on the basis of the result detected by the acceleration detection device.
Or, the tendency of initiating the automatically pressurizing control for the steering control by braking can be determined especially on the basis of a turning condition of the vehicle, out of the conditions of vehicle motion. Therefore, the vehicle motion control system may further comprise a turning condition detection device for detecting the turning condition of the vehicle. In this case, the controller may be adapted to modify the time period at least on the basis of the result detected by the turning condition detection device.
Furthermore, in the case where the automatic hydraulic pressure generating apparatus includes a vacuum booster, intake vacuum of an engine mounted on the vehicle can be a pressure source for the automatically pressurizing control. When the intake vacuum is relatively large, therefore, a relatively short period of the delay control may be sufficient. Accordingly, the vehicle motion control system may further comprise a vacuum detection device for detecting the intake vacuum of the engine. In this case, the controller may be adapted to modify the time period at least on the basis of the result detected by the vacuum detection device.
Preferably, the vehicle motion control system includes wheel brake cylinders which are operatively associated with wheels of the vehicle, respectively, an automatic hydraulic pressure generating apparatus for generating a hydraulic braking pressure irrespective of operation of a brake pedal, a hydraulic pressure control valve device which is disposed between the pressure generating apparatus and the wheel brake cylinders to control the hydraulic braking pressure in each wheel brake cylinder, an acceleration detection device for detecting an accelerating condition of the vehicle, a braking operation detection device for detecting a braking operation of the vehicle, and a controller for controlling the pressure generating apparatus and the valve device in response to conditions of vehicle motion, and performing an automatically pressurizing control to the wheel brake cylinders at least when a brake pedal is not depressed, to perform a vehicle motion control. The controller is adapted to maintain the pressure generating apparatus to operate for a predetermined time period after the vehicle motion control was terminated, and control the valve device to shut off the communication between the pressure generating apparatus and the wheel brake cylinders. And, the controller is adapted to control the pressure generating apparatus to be in an inoperative condition thereof, and control the valve device to release the shut-off condition between the pressure generating apparatus and the wheel brake cylinders, in response to a result detected by at least one of the acceleration detection device and the braking operation detection device.
In the above-described vehicle motion control system, preferably, the controller is adapted to make the pressure generating apparatus to be in an operative condition thereof, and control the valve device to shut off the communication between the pressure generating apparatus and the wheel brake cylinders, when the acceleration detection device has detected the acceleration, or when the braking operation detection device has not detected the braking operation, during the predetermined time period after the vehicle motion control was terminated, and the controller is adapted to make the pressure generating apparatus to be in an inoperative condition thereof, and control the valve device to release the shut-off condition between the pressure generating apparatus and the wheel brake cylinders, when the acceleration detection device has not detected the acceleration, or when the braking operation detection device has detected the braking operation, during the predetermined time period after the vehicle motion control was terminated.
In the above-described vehicle motion control system, the pressure generating apparatus may include a master cylinder and a vacuum booster or a hydraulic booster.